WINTER  INJURY  TO  YOUHG  WAL- 
NUT TREES  DURING  1921-1922 

By 
L.  D.  Batohelor. 


UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 
AGRICULTURAL   EXPERIMENT   STATION 

CIRCULAR  No.  234 
MAKCH,  1922 

WINTER  INJURY  TO  YOUNG  WALNUT  TREES 
DURING   1921-1922 

BY  L.  D.  BATCHELOE 


Unfavorable  soil  of  climatic  conditions  which  show  little  or  no 
effect  upon  many  species  of  orchard  trees  may  seriously  injure,  if  not 
actually  kill,  walnut  trees.  The  effect  of  such  unfavorable  conditions 
is  often  first  clearly  manifested  in  the  early  spring,  hence  this  class 
of  troubles  is  generally  known  as  winter  injury.  During  March  and 
April  the  tops  of  healthy  trees  make  rapid  growth,  whereas  the  tops 
of  injured  trees  show  no  growth  whatever.  Frequently  unfavorable 
conditions  not  only  cause  the  death  of  the  uppermost  twigs  but  also 
of  some  of  the  older  branches.  In  extreme  cases  the  trees  may  be 
killed  nearly  to  the  ground. 

One  of  the  most  common  causes  of  winter  injury  to  walnut  trees 
is  the  early  fall  frosts  which  may  occur  before  the  trees  are  dormant. 
Young  trees  are  more  likely  to  suffer  from  early  frosts  than  mature 
bearing  trees,  because  the  latter  become  dormant  earlier  in  the  season. 
Walnut  foliage  which  is  still  green  and  shows  no  sign  of  its  normal 
autumn  color  is  apparently  as  subject  to  frost  injury  as  tender  vege- 
tables. The  frosted  foliage  drops  prematurely,  and  hence  the  green, 
immature  twigs  are  fully  exposed  to  the  sun's  heat  during  bright 
days  in  fall  and  winter.  The  moisture  loss  following  the  dropping  of 
the  leaves  is  much  more  rapid  from  the  succulent  twigs  than  from  the 
more  mature  growth. 

In  many  cases  the  twigs  themselves  show  no  actual  injury  at  the 
time  of  the  frost,  but  are  eventually  killed  and  show  a  marked  sun- 
burning  following  the  loss  of  the  leaves.  Such  prematurely  defoliated 
twigs  usually  begin  to  show  injury  from  sunburning  about  the  middle 
of  January.  By  early  spring  more  or  less  of  the  new  growth  is  dead. 
In  occasional  instances,  however,  a  portion  of  the  north  side  of  twigs 
thus  injured  may  remain  healthy  and  produce  normal  growth  the 
following  spring.  The  death  of  the  immature  twigs  is  apparently 

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due,  not  so  much  to  the  initial  low  temperature  which  killed  the  leaves, 
as  to  the  subsequent  sunburning.  Vertical  young  shoots  frequently 
show  discolorations  due  to  sunburning  on  the  south  side,  throughout 


Fig.  1. — Three-year-old  walnut  tree  killed  nearly  to  the  ground  by  early  fall 
frosts. 

their  entire  length,  while  horizontal  or  oblique  branches  usually  show 
this  sunburned  area  more  strikingly,  but  on  the  upper  sides  only. 
Such  a  sunburned  appearance  of  the  young  limbs  in  the  spring  is  a 
prevailing  characteristic  of  trees  which  have  been  only  mildly  frosted 
tho  previous  fall  before  the  trees  were  dormant.  If  the  young  trees 


CIRCULAR  234]      WINTER  INJURY  TO  WALNUT  TREES,  1921-22 


3 


are  very  actively  growing  when  the  early  frosts  occur,  or  if  the  first 
frost  is  especially  severe,  the  injury  may  be  pronounced  in  the  trunk 
as  well  as  the  limbs  of  trees  one  to  five  years  old.  In  such  severe  cases 
the  trees  die  back  within  a  few  inches  of  the  ground.  A  tree  thus 
affected  is  shown  by  figure  1.  Inasmuch  as  the  root  systems  are  not 


Fig.   2. — A  two-year-old  walnut  tree  regrown  from  a  sprout  which  came  out 
on  original  winter  injured  tree  three  inches  from  the  ground. 

injured  by  this  condition,  frosted  and  sunburned  trees,  as  a  general 
rule,  produce  a  rank,  succulent  twig  growth  from  the  base  of  the  main 
branches,  the  trunk,  or  the  crown,  depending  on  the  injury,  the  summer 
following  the  initial  injury.  Such  growth  in  turn  is  less  likely  to 
mature  early  and  more  likely  to  be  injured  by  autumn  frosts  than  the 
normal  tree.  When  the  cycle  of  events  just  described  becomes  estab- 
lished it  thus  tends  to  perpetuate  itself. 

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The  fall  of  1921  was  an  especially  bad  season  for  young  walnut 
groves.  The  first  fall  frost  did  not  come  much  earlier  than  normaf, 
but  it  was  much  more  severe  than  usual.  The  Hemet  and  San  Jacinto 
valleys  may  be  taken  as  an  example  of  what  occurred  in  many  of  the 
lower  lying  walnut  areas.  During  a  period  of  nineteen  years  the 
average  date  for  the  first  killing  frost  in  the  autumn  in  San  Jacinto 
is  November  24.  The  first  frosts  are  usually  light,  with  absolute 
minimum  temperatures  of  27°  or  28°  F. 

During  the  fall  of  1921  the  first  killing  frost  in  the  San  Jacinto 
and  Hemet  sections  occurred  on  the  night  of  November  17.  A  thermo- 
graphic  record  in  a  walnut  grove  showed  that  a  temperature  of  26°  F. 
occurred  by  11  o'clock  on  the  night  of  the  17th,  and  that  it  kept  grow- 
ing colder  until  daylight  on  the  18th,  when  the  minimum  temperature 
reached  20°  F.  *  The  minimum  temperatures  on  the  19th  and  20th  were 
20°  and  23°  respectively.  This  degree  of  cold  was  sufficient  to  turn 
all  the  walnut;  leaves  brown  and  crisp  even  though  the  trees  had 
started  to  become  dormant  to  the  extent  that  the  leaves  were  turning 
a  yellowish  green  before  the  frost. 

Judging  by  the  appearance  of  some  of  the  young  trees  thus  far 
examined  the  current  spring,  the  most  pronounced  injury  may  be  in 
the  trunks.  The  entire  cambium  layer  of  the  trunks  in  many  cases 
has  turned  black  and  the  trees  are  dead  to  within  a  few  inches  of  the 
ground.  Meanwhile  the  small  branches  may  show  less  apparent  in- 
jury than  the  trunks.  Many  cases  have  been  noted  during  this  season, 
and  also  previous  ones,  where  trees  completely  dead  in  the  tops  and 
most  of  the  trunk  showed  a  normal  condition  of  the  cambium  layer 
1  to  3  inches  from  the  surface  of  the  ground  and  a  normal  condition 
of  the  roots.  Trees  which  are  thus  severely  injured  should  not  be 
pulled  out  and  destroyed,  inasmuch  as  many  of  them  will  probably 
sprout  above  the  bud  and  a  new  tree  can  be  trained  into  shape  from 
such  a  sprout.  If  more  than  one  sprout  starts  out  from  the  base,  the 
terminal  buds  on  all  but  one  should  be  pinched  out  and  the  most  up- 
right sprout  retained  for  the  future  tree.  An  English  walnut  sprout 
may  be  seen  among  the  black  walnut  sprouts  in  figure  1.  Trees  which 
are  regrown  in  this  manner  should  be  supported  during  the  first  one 
or  two  seasons'  growth.  This  may  be  accomplished  by  tying  them  to 
the  dead  trunk,  or,  better,  by  tying  them  to  a  2"  X  2"  stake,  which 
should  be  5  or  6  feet  high.  The  tree  shown  in  figure  2  has  been  re- 
formed from  a  sprout  which  came  out  of  the  original  tree  at  the  curve 
in  the  trunk,  about  3  inches  from  the  ground.  The  newly  formed  top 
is  now  two  years  old.  Numerous  young  orchards  have  been  severely 
injured  in  the  past ;  the  trouble  was  especially  bad  during  the  winter 


CIRCULAR  234]       WINTER  INJURY  TO  WALNUT  TREES,  1921-22  5 

of  1916-17,  and  again  during  1919-20.  By  patience  and  persistence 
-nany  such  plantings  have  been  regrown  from  the  original  trees  at 
small  expense,  except  the  loss  in  time.  Figure  3  shows  an  example 
of  this  experience. 

Injury  from  frost  may  be  prevented  if  it  is  possible  to  mature  the 
young  walnut  trees  early  in  the  autumn  so  that  the  leaves  will  turn 
yellow  and  normally  fall  from  the  tree  before  the  first  early  frosts, 
which  frequently  occur  from  the  1st  to  the  15th  of  November  in  many 
of  the  lowlands  in  southern  California.  Early  maturity  can  be  pro- 


Fig.  3. — This  young  orchard  was  killed  nearly  to  the  ground  by  frosts  in  the 
fall  of  1916.  By  persistence  and  patience  the  owner  has  regrown  most  of  these 
trees,  until  it  is  now  a  creditable  young  orchard. 

moted  by  withholding  irrigation  water  in  the  late  summer  and  early 
fall.  Trees  which  are  not  irrigated  after  August  15  may  be  expected 
to  mature  earlier  than  trees  watered  in  late  August  and  September. 
During  the  past  season  of  abnormal  severity  of  the  early  fall  frosts 
the  above  precaution  was  not  always  successful,  especially  in  low 
frosty  sites,  on  clean  cultivated  land,  or  where  the  August  irrigation 
was  particularly  heavy.  The  young  walnut  trees  interplanted  with 
vegetable  crops  which  ripened  in  the  early  fall,  and  thus  took  much 
of  the  soil  moisture  from  the  trees,  thereby  maturing  them  somewhat 
prematurely,  are  the  least  affected  by  the  frost  injury  the  current 
season.  It  is  doubtful  if  any  precautionary  cultural  or  irrigation 
practice  could  have  prevented  a  great  deal  of  the  damage  which  has 
been  experienced  this  abnormal  seasqi 


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DIVISION  OF  SUBTROPICAL  HORTICULTURE 

COLLEGE  OF  AGRICULTURE 

BERKELEY,  CALIFORNIA 


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185.  Report  of  Progress  in  Cereal  Investiga-  299. 

tions.  300. 

241.  Vine  Pruning  in  California,  Part  I.  304. 
246.  Vine  Pruning  in  California,  Part  II. 

251.  Utilization  of  the  Nitrogen  and  Organic  308. 

Matter    in    Septic    and    Imhoff    Tank 

Sludges. 

253.  Irrigation    and    Soil    Conditions    in    the  309.  I 

Sierra  Nevada  Foothills,  California. 

261.  Melaxuma  of  the  Walnut,  "Juglans  regia."  310. 

262.  Citrus    Diseases    of    Florida    and    Cuba  312. 

Compared  with  Those  of  California.  313. 

263.  Size  Grades  for  Ripe  Olives.  316. 

266.  A  Spotting  of  Citrus  Fruits  Due  to  the  317. 

Action  of  Oil  Liberated  from  the  Rind.  318, 

267.  Experiments  with  Stocks  for  Citrus.  320. 

268.  Growing  and  Grafting  Olive  Seedlings.  321. 

270.  A  Comparison  of  Annual  Cropping,   Bi-  323. 

ennial   Cropping,    and    Green    Manures 

on  the  Yield  of  Wheat.  324. 

271.  Feeding  Dairy  Calves  in  California. 

273.  Preliminary  Report  on  Kearney  Vineyard  325. 
Experimental  Drain. 

275.  The   Cultivation  of   Belladonna  in   Cali- 

fornia. 328. 

276.  The  Pomegranate.  330. 

278.  Grain  Sorghums.  331. 

279.  Irrigation  of  Rice  in  California.  332. 

280.  Irrigation   of  Alfalfa  in  the   Sacramento  334. 

Valley. 

282.  Trials   with   California   Silage   Crops  f  or  335. 

Dairy  Cows. 

283.  The  Olive  Insects  of  California.  336. 

285.  The  Milk  Goat  in  California. 

286.  Commercial  Fertilizers.  337. 

287.  Vinegar  from  Waste  Fruits.  339. 
294.  Bean  Culture  in  California. 

297.  The  Almond  in  California.  340. 

298.  Seedless  Raisin  Grapes. 


The  Use  of  Lumber  on  California  Farms. 
Commercial  Fertilizers. 
A   Study   on   the   Effects   of   Freezes   on 
Citrus  in  California. 


Acid 


igat 
.     II. 


Physical  and  Chemical  Pro- 


perties of  Liquid  Hydrocyanic  Acid. 

.  The  Carob  in  California.  II.  Nutritive 

Value  of  the  Carob  Bean. 
Plum  Pollination. 
Mariput  Barley. 

Pruning  Young  Deciduous  Fruit  Trees. 
The  Kaki  or  Oriental  Persimmon. 
Selections  of  Stocks  in  Citrus  Propagation. 
The  Effects  of  Alkali  on  Citrus  Trees. 
Control  of  the  Coyote  in  California. 
Commercial  Production  of  Grape  Syrup. 
Heavy  vs.  Light  Grain  Feeding  for  Dairy 

Cows. 
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Temperatures. 
Rice    Irrigation    Measurements   and    Ex- 

periments in  Sacramento  Valley,   1914- 

1919. 

Prune  Growing  in  California. 
Dehydration  of  Fruits. 
Phylloxera-Resistant  Stocks. 
Walnut  Culture  in  California. 
Preliminary  Volume  Tables  for   Second- 

Growth  Redwoods. 
Cocoanut  Meal  as  a  Feed  for  Dairy  Cows 

and  Other  Livestock. 
The  Preparation  of  Nicotine  Dust  as  an 

Insecticide. 

Some  Factors  of  Dehydrater  Efficiency. 
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Small  and  Large  Timber. 
Control  of  the  Pocket  Gopher  in  California  . 


No. 

70.  Observations  on  the  Status  of  Corn 
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82.  The  Common  Ground  Squirrels  of  Cali- 
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87.  Alfalfa. 

1 10.  Green  Manuring  in  California. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 

fornia Soils. 

113.  Correspondence  Courses  in  Agriculture. 
115.  Grafting  Vinif era  Vineyards. 

126.  Spraying  for  the  Grape  Leaf  Hopper. 

127.  House  Fumigation. 

128.  Insecticide  Formulas. 

129.  The  Control  of  Citrus  Insects. 

130.  Cabbage  Growing  in  California. 
135.  Official  Tests  of  Dairy  Cows. 
138.  The  Silo  in  California  Agriculture. 

144.  Oidium  or  Powdery  Mildew  of  the  Vine. 
148.  "Lungworms." 

151.  Feeding  and  Management  of  Hogs. 

152.  Some  Observations  on  the  Bulk  Handling 

of  Grain  in  California. 

153.  Announcement    of    the    California    State 

Dairy  Cow  Competition,  1916-18. 

154.  Irrigation     Practice    in    Growing    Small 

Fruits  in  California. 

155.  Bovine  Tuberculosis. 

157.  Control  of  the  Pear  Scab. 

158.  Home  and  Farm  Canning. 

159.  Agriculture  in  the  Imperial  Valley. 

160.  Lettuce  Growing  in  California. 

161.  Potatoes  in  California. 

164.  Small  Fruit  Culture  in  California. 


CIRCULARS 

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166. 
167. 
168. 


172. 
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175. 


177. 
17S. 
179. 

181. 

182. 

183. 

184. 
188. 
189. 
190. 


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under  California  Conditions. 
The  County  Farm  Bureau. 
Feeding  Stuffs  of  Minor  Importance. 
Spraying  for  the  Control  of  Wild  Morning- 

Glory  within  the  Fog  Belt. 
The  1918  Grain  Crop. 
Fertilizing  California  Soils  for  the   1918 

Crop. 

Wheat  Culture. 

The  Construction  of  the  Wood-Hoop  Silo. 
Farm  Drainage  Methods. 
Progress   Report  on   the   Marketing  anS 

Distribution  of  Milk. 
Hog  Cholera  Prevention  and  the  Serum 

Treatment. 
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The  Packing  of  Apples  in  California. 
Factors  of  Importance  in  Producing  Milk 

of  Low  Bacterial  Count. 
Control  of  the  California  Ground  Squirrel. 
Extending  the  Area  of  Irrigated  Wheat  in 

California  for  1918. 
Infectious  Abortion  in  Cows. 
A  Flock  of  Sheep  on  the  Farm. 
Lambing  Sheds. 
Winter  Forage  Crops. 
Agriculture  Clubs  in  California. 
A  Study  of  Farm  Labor  in  California. 


3.  Syrup  from  Sweet  Sorghum. 
1.  Helpful  Hints  to  Hog  Raisers. 


County  Organizations  for  Rural  Fire  Con- 
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